The invention concerns an apparatus for applying a surface coating to cores.
A device of this type is known from EP-A-0 744 212.
In practical operation, in the case of the known device, in particular in the case of oblong shaped items, not to be excluded is that these items that frequently display rectilinear lateral surface have contact with one another over a longer line, or even over a greater area. With the circulating movement of the product inside the drum, the fluidly applied coating in the case of this type of intensive contact of two adjacent items can lead to their adhering to each other, in particular since, in practice, frequently found within the circulated product is a xe2x80x9cdead zonexe2x80x9d in the center of the product, inside of which the items are hardly moved. In the case of the known device, to minimize this region the drum is embodied with an axial length that is greater than to the diameter of the drum, so that obtained overall is an oblong cylinder. By means of this oblong embodiment, the product is distributed over a greater length of the cylinder, so that the circulated bed of the product displays at its interior a small xe2x80x9cdead zone.xe2x80x9d
Known from FR-A-1 459 246 is a coating apparatus whose drum displays first carriers that do not impart to the product any forward feed in the axial direction of the drum, hence produce no axial transport, rather transporting the product exclusively transversely to the axis of the drum in a rotary movement about the drum axis, hence in the form of a circulation or circumferential transport. Second carriers are provided spaced inwardly out from the drum wall and produce an axial transport of the product inside the drum in the longitudinal direction of the drum. Since the drum is disposed horizontally, axial transport of the coating product is effected exclusively through the second carriers.
The object of the invention is to improve an apparatus of this genre such that it assures as thorough as possible circulation of the product.
The object of the invention is met through an apparatus with a rotatably mounted drum for accepting the cores, with at least one spray nozzle for deposit of the surface material onto the core, as well as with a heating device for the inside space of the drum, as well as with an inlet and an outlet opening, as well as with canters arranged in the drum cores, characterized by the fact that the drum (7) is embodied as an oblong cylinder, and that second carriers (12) are provided for the cores, which transport the cores in a direction opposed to the direction of the first carriers (11), and that are radially offset relative to the first carriers (11), and that the drum (7) is journaled in the apparatus (1) in quickly removable fashion.
In other words, additionally to the first carriers lying inside at the pheriphery of the drum, which transport the product in one direction along the longitudinal axis of the drum, the invention proposes to provide opposed-acting second carriers that are not arranged alternately but rather are radially offset, for example further toward the interior of the drum. Since these carriers are supported on brackets against the drum wall, the product can be transported under these carriers along the drum wall by the first carriers. However, the regions of the product having a greater layer thickness are picked up by the second carriers, and since these second carriers act in opposed fashion with the first carriers a more intensive, thorough mixing of the bed is effected, so that a xe2x80x9cdead zonexe2x80x9d can be minimized, and, depending upon the geometry of the carriers and the drum, can be practically regularly excluded, namely if the coating results yield no items stuck together.
Designated as cylinders within the idea of this invention are not only drum shapes with a circular cross section, but also with a polygonal, for example an octagonal cross section.
The drum can advantageously be planned to be removably mounted in the apparatus. In this manner, even in operation of the apparatus with only one drum, a high degree of system availability can be assured, namely in that a soiled drum, even in the case of considerable expense and correspondingly great time requirement, can be replaced within a short time with a cleaned drum. Hence, the cleaning times, with comparatively low financial expense through procurement of a single replacement drum, do not correspond to the down times of the entire apparatus, so that, all together, the apparatus can be operated with considerably improved economy.
The drum can advantageously be planned to be tiltably supported in its longitudinal axis so that it can be operated in a slanted arrangement. In this manner, automatically assured is that the items inside the drum will be optimally, thoroughly mixed and again always picked up by the carriers and moved through each other.
Advantageously, the first, upwardly-transporting carriers in the case of this type of diagonal operation of the drum can be arranged, in a manner known per se, along the drum wall, while the second, opposed-transporting carriers are supported against the drum wall, and are correspondingly radially further inside. In this way, the drum, in a manner known per se, can be embodied in more price-favorable fashion, and the second carriers can be added later.
With corresponding space planning, the apparatus can advantageously display several drums that operate connected one after another, so that the individual coating steps can run off after one another in a drum that is special for each step. In this manner, optimal treatment conditions can be set in the individual drums; the degree of soiling of each one of the drums can be correspondingly reduced.